The present invention relates, in general, to an electromotoric operating mechanism, such as a single drive or dual drive, for height adjustment of an article of furniture, especially for furniture items useful in the field of hospitals and/or nursing, and more particularly relates to an operating mechanism of a type including an adjusting spindle actuated by a drive having a worm wheel and having mounted thereon a spindle nut which interacts with a link member in fixed rotative engagement on a shaft of an adjustable piece of furniture, with the driving relationship between the output pin of the drive and the adjusting spindle being disengageable.
An electromotoric operating mechanism for this type is applicable for a wide variety of different articles of furniture, for example beds, slatted bed frames or the like. Normally, elevating and lowering of the respective furniture component is realized at a relatively slight speed when the electromotoric operating mechanism is turned on. However, in particular hospitals or nursing homes demand occasionally a lowering of the adjustable furniture item at a significantly higher speed. Various constructions have been proposed to mechanically disengage the drive train between the output pin of the drive and the adjusting spindle.
A conventional operating mechanism includes the disposition of a first clutch disk in fixed rotative engagement on the output pin of the drive. A second clutch disk is wedged in fixed rotative engagement onto the associated end of the adjusting spindle. Both clutch disks are brought into engagement by a coupling sleeve which travels in axial direction. The clutch disk mounted on the output pin and the coupling sleeve have complementary teeth of asymmetric configuration so that the coupling sleeve is driven in synchronism by the first clutch disk when the furniture item is raised by the drive, and turns idle when the furniture item is adjusted by hand in a same direction while the first clutch disk is at a standstill.
This conventional construction suffers the drawback of requiring a relatively large number of components in order to realize the disengagement of the drive train. Moreover, as the coupling sleeve embraces the second clutch disk, the drive exhibits a substantial size. Operating systems for articles of furniture are marketed in large numbers so that cost-efficiency is of great concern.